Document processing apparatus with rotatable gap sensor

ABSTRACT

A document processing apparatus includes a sheet passageway, a sheet-feeding mechanism and a rotatable gap sensor. The sheet-feeding mechanism transports a first sheet and a second sheet successively through the sheet passageway. The rotatable gap sensor is rotated by movement of the first sheet and the second sheet for the detection of the presence of the first sheet and the second sheet. The rotatable gap sensor generates a plurality of state signals with respect to rotating states of the rotatable gap sensor.

This application claims priority of No. 097136792 filed in Taiwan R.O.C. on Sep. 25, 2008 under 35 USC 119, the entire content of which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a document processing apparatus, and more particularly to a document processing apparatus having a rotatable gap sensor which can detect presence or absence of a sheet.

2. Related Art

In an automatic document feeder of a document processing apparatus such as a scanner, a single sensor or a number of sensors are usually installed to detect a leading edge and a trailing edge of a document. The sensor outputs a signal to inform a processor of the scanner of a position of the document so that an image of the document may be precisely acquired, or transportation of two successive documents may be precisely controlled. With the precise control of the transportation, an interval between two successive documents can be minimized and the time required for scanning a stack of documents can be thus shortened.

Conventionally, the sensor comprises a swingable rocker arm for the detection of the presence or absence of a document. The sensor generates a sensing signal to the processor only when the rocker arm is rocked by the document greater than a certain angle. This sensor works well at a normal scanning speed, but cannot come up with a high scanning speed due to its poor response time. Thus, at the high scanning speed, the temporal precision of the scanner and the quality of the acquired image of the document are degraded. In addition, due to the poor response time of the sensor, the sensor also cannot distinguish between two successive documents which are very close to each other.

Therefore, it is an important subject of the invention to provide a document sensor, which can work well at the high scanning speed.

SUMMARY OF THE INVENTION

It is therefore an object of the invention to provide a document processing apparatus having a rotatable gap sensor which has a shorter response time so that documents can be well and precisely processed when the documents are transported at the high speed.

To achieve the above-identified object, the invention provides a document processing apparatus including a sheet passageway, a sheet-feeding mechanism and a rotatable gap sensor. The sheet-feeding mechanism transports a first sheet and a second sheet successively through the sheet passageway. The rotatable gap sensor is rotated by movement of the first sheet and the second sheet for the detection of the presence of the first sheet and the second sheet. The rotatable gap sensor generates a plurality of state signals with respect to rotating states of the rotatable gap sensor.

Further scope of the applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention.

FIG. 1 is a schematic illustration showing a document processing apparatus having a rotatable gap sensor according to a first embodiment of the invention.

FIGS. 2 and 3 show two examples of the rotatable gap sensor of FIG. 1.

FIG. 4 shows two waveforms of the state signals output by the rotatable gap sensor.

FIG. 5 is a schematic illustration showing a rotatable gap sensor according to a second embodiment of the invention.

FIG. 6 is a pictorial view showing a rotatable gap sensor according to a third embodiment of the invention.

FIG. 7 is a schematic illustration showing a rotatable gap sensor according to a fourth embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will be apparent from the following detailed description, which proceeds with reference to the accompanying drawings, wherein the same references relate to the same elements.

FIG. 1 is a schematic illustration showing a document processing apparatus having a rotatable gap sensor according to a first embodiment of the invention. Referring to FIG. 1, the document processing apparatus of this embodiment, which may be a scanner, a printer, a multi-function peripheral, a copier, or the like, includes a housing 10, a sheet passageway 20, a sheet-feeding mechanism 30 and a rotatable gap sensor 40.

The housing 10 is usually a housing of an automatic sheet feeder, and may also include a housing of a scanner or a printer. The sheet passageway 20 is formed in the housing 10. The sheet-feeding mechanism 30 disposed in the housing 10 transports a first sheet S1 and a second sheet S2 successively through the sheet passageway 20.

In this embodiment, the sheet-feeding mechanism 30 includes a frictional element 31, a separation roller 32 and rollers 33, 34, 35 and 36. The frictional element 31 and the separation roller 32 cooperate with each other to perform sheet separation. In addition, the sheet-feeding mechanism 30 may further include a pickup roller (not shown), and the pickup roller picks up the sheet placed in a supply tray and feeds the sheet to the frictional element 31 and the separation roller 32.

The rotatable gap sensor 40 is mounted on the housing 10 and detects presence of the first sheet S1 and the second sheet S2. The rotatable gap sensor 40 is rotated by movement of the first sheet S1 and the second sheet S2 and generates a plurality of state signals with respect to rotating states of the rotatable gap sensor 40.

In this embodiment, the document processing apparatus is a scanner. Therefore, the document processing apparatus may further include a scan module 50, a supply tray 80 and a control circuit 60. The scan module 50 acquires, through a transparent platen 12, images of the sheets transported past a scan region 22.

The scan module 50 is disposed in the housing 10 and acquires the images of the first sheet S1 and the second sheet S2. The scan module 50 may comprise a charge-coupled device (CCD) sensor or a contact image sensor (CIS). In this embodiment, the scan module 50 is a CCD scan module including a light source 51, a reflecting mirror 52, a lens 53 and an image sensor 54. The scan module 50 may be moved back and forth along a guiding rod 14.

The supply tray 80 supports the first sheet S1 and the second sheet S2 to be transported.

The control circuit 60 is electrically connected to the sheet-feeding mechanism 30 and the rotatable gap sensor 40 and controls the sheet-feeding mechanism 30 to start to transport the second sheet S2 into the sheet passageway 20 according to the state signals generated in response to the detection of the first sheet S1. In addition, the control circuit 60 may also be electrically connected to the scan module 50, the sheet-feeding mechanism 30 and the rotatable gap sensor 40, and controls the scan module 50 to start to scan the first sheet S1 and the second sheet S2 according to the state signals.

FIGS. 2 and 3 show two examples of the rotatable gap sensor 40 of FIG. 1. Referring to FIG. 2, the rotatable gap sensor 40 of this example includes a roller 41 and a transmissive optical detector 43. The roller 41 has a plurality of through holes 42 and is rotated by the movement of the first sheet S1 and the second sheet S2 through contact with the first sheet S1 and the second sheet S2. The roller 41 comprises a rim 41A for contacting the first sheet S1 and the second sheet S2, and the rim 41 of the roller 41 is provided with a high friction surface so that the roller 41 can be rotated by the movement of the first sheet S1 and the second sheet S2. The transmissive optical detector 43 is disposed on either side of the roller 41 and emits an optical signal SS and receives the optical signal SS penetrating through the through holes 42. In FIG. 2, the transmissive optical detector 43 may include a photo-interrupter, which has a transmitting end 43A and a receiving end 43B. The transmitting end 43A emits the optical signal SS, and the receiving end 43B receives the optical signal SS penetrating through the through holes 42.

Referring to FIG. 3, this second example is similar to that of FIG. 2 except that the rotatable gap sensor 40′ includes a roller 41 and a reflective optical detector 45. The roller 41 has a plurality of reflective blocks 44. The reflective optical detector 45 is disposed on one side of the roller 41 and emits an optical signal SS and receives the optical signal SS reflected by the reflective blocks 44. The reflective optical detector 45 includes a transmitting end 45A and a receiving end 45B. The transmitting end 45A emits the optical signal SS, and the receiving end 45B receives the optical signal SS reflected by the reflective blocks 44.

FIG. 4 shows two waveforms of the state signals output by the optical detector 43 or 45 of the rotatable gap sensor at time of detection. As shown in FIG. 4, state signals SR1 and SR2 output by the optical detector 43 or 45 have different waveforms from time t1 to time t2. The state signal SR1 indicates that a gap between two successive sheets is detected from time t1 to time t2. On the other hand, the state signal SR2 indicates that no gap between sheets is detected.

FIG. 5 is a schematic illustration showing a rotatable gap sensor according to a second embodiment of the invention. As shown in FIG. 5, this embodiment is similar to the first embodiment except that the rotatable gap sensor 40/40′ further includes a pressing roller 46 disposed opposite the roller 41. The pressing roller 46 presses the first sheet S1 and the second sheet S2 against the roller 41.

FIG. 6 is a pictorial view showing a rotatable gap sensor 70 according to a third embodiment of the invention. Referring to FIG. 6, the rotatable gap sensor 70 of this embodiment includes a shaft 71, a roller 72, an encoding disk 73 and a transmissive optical detector 75. The roller 72 is mounted on the shaft 71 and is rotated by the movement of the first sheet S1 and the second sheet S2 through contact with the first sheet S1 and the second sheet S2. The encoding disk 73 is mounted on the shaft 71 and is rotated in synchronicity with the roller 72. The encoding disk 73 is provided with a plurality of through holes 74. The transmissive optical detector 75 is disposed on either side of the encoding disk 73 and emits an optical signal SS and receives the optical signal SS penetrating through the through holes 74.

The transmissive optical detector 75 includes a photo-interrupter, which includes a transmitting end 75A and a receiving end 75B. The transmitting end 75A emits the optical signal SS and the receiving end 75B receives the optical signal SS penetrating through the through holes 74. The photo-interrupter is mounted on a circuit board 78, and the circuit board 78 is provided with a connector 79 so that the circuit board 78 can be electrically connected to a mainboard (not shown).

FIG. 7 is a schematic illustration showing a rotatable gap sensor 70′ according to a fourth embodiment of the invention. As shown in FIG. 7, the rotatable gap sensor 70′ of this embodiment is similar to the rotatable gap sensor 70 of the third embodiment. Specifically speaking, the rotatable gap sensor 70′ includes a shaft 71, a roller 72, an encoding disk 73′ and a reflective optical detector 77. The roller 72 is mounted on the shaft 71 and is rotated by the movement of the first sheet S1 and the second sheet S2 through contact with the first sheet S1 and the second sheet S2. The encoding disk 73′ is mounted on the shaft 71 and is rotated in synchronicity with the roller 72. The encoding disk 73′ is provided with a plurality of reflective blocks 76. The reflective optical detector 77 includes a transmitting end 77A and a receiving end 77B and is disposed on one side of the encoding disk 73′. The transmitting end 77A emits an optical signal SS, and the receiving end 77B receives the optical signal SS reflected by the reflective blocks 76.

In the embodiments of the invention, it is disclosed that the roller of the rotatable gap sensor is disposed in the sheet passageway and a friction force between the sheet and the roller rotates the roller. The roller is rotated by the movement of the sheet and becomes stationary when no sheet presents. In other words, the rotating states of the roller depend on whether a sheet is present or not. The optical signals are received by the optical detector of the rotatable gap sensor based on the rotating states of the roller, and corresponding state signals are generated by the optical detector. The position information of the sheet can be obtained from the state signals so that the control circuit controls the sheet-feeding mechanism and the scan module based on the position information. The rotatable gap sensor disclosed in the invention has a shorter response time than a conventional sensor comprising a rocker arm, so transportation and scanning of the sheet can be precisely controlled even at a high processing speed, and thus the quality of the acquired images can be maintained.

While the invention has been described by way of examples and in terms of preferred embodiments, it is to be understood that the invention is not limited thereto. To the contrary, it is intended to cover various modifications. Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications. 

1. A document processing apparatus, comprising: a sheet passageway; a sheet-feeding mechanism, for transporting a first sheet and a second sheet successively through the sheet passageway; and a rotatable gap sensor, for detecting presence of the first sheet and the second sheet, the rotatable gap sensor being rotated by movement of the first sheet and the second sheet, and for generating a plurality of state signals with respect to rotating states of the rotatable gap sensor.
 2. The apparatus according to claim 1, further comprising: a control circuit, electrically connected to the sheet-feeding mechanism and the rotatable gap sensor, for controlling the sheet-feeding mechanism to start to transport the second sheet into the sheet passageway according to the state signals generated in response to the detection of the first sheet.
 3. The apparatus according to claim 1, further comprising: a scan module, for acquiring images of the first sheet and the second sheet.
 4. The apparatus according to claim 3, further comprising: a control circuit, electrically connected to the scan module, the sheet-feeding mechanism and the rotatable gap sensor, for controlling the scan module to start to scan the first sheet and the second sheet according to the state signals.
 5. The apparatus according to claim 1, wherein the rotatable gap sensor comprises: a roller, provided with a plurality of through holes, the roller being rotated by the movement of the first sheet and the second sheet through contact with the first sheet and the second sheet; and a transmissive optical detector, disposed on either side of the roller, for emitting an optical signal and receiving the optical signal penetrating through the through holes.
 6. The apparatus according to claim 5, wherein the rotatable gap sensor further comprises: a pressing roller, disposed opposite the roller, for pressing the first sheet and the second sheet against the roller.
 7. The apparatus according to claim 5, wherein the roller comprises a rim for contacting the first sheet and the second sheet, and the rim is provided with a high friction surface.
 8. The apparatus according to claim 5, wherein the transmissive optical detector comprises a photo-interrupter.
 9. The apparatus according to claim 8, wherein the photo-interrupter comprises a transmitting end for emitting the optical signal and a receiving end for receiving the optical signal.
 10. The apparatus according to claim 1, wherein the rotatable gap sensor comprises: a roller, provided with a plurality of reflective blocks, the roller being rotated by the movement of the first sheet and the second sheet through contact with the first sheet and the second sheet; and a reflective optical detector, disposed on one side of the roller, for emitting an optical signal and receiving the optical signal reflected by the reflective blocks.
 11. The apparatus according to claim 10, wherein the rotatable gap sensor further comprises: a pressing roller, disposed opposite the roller, for pressing the first sheet and the second sheet against the roller.
 12. The apparatus according to claim 10, wherein the roller comprises a rim for contacting the first sheet and the second sheet, and the rim is provided with a high friction surface.
 13. The apparatus according to claim 10, wherein the reflective optical detector comprises a transmitting end for emitting the optical signal and a receiving end for receiving the optical signal.
 14. The apparatus according to claim 1, further comprising: a supply tray for supporting the first sheet and the second sheet to be transported.
 15. The apparatus according to claim 1, wherein the rotatable gap sensor comprises: a shaft; a roller, mounted on the shaft and rotated by the movement of the first sheet and the second sheet through contact with the first sheet and the second sheet; an encoding disk, mounted on the shaft and rotated in synchronicity with the roller, the encoding disk being provided with a plurality of through holes; and a transmissive optical detector, disposed on either side of the encoding disk, for emitting an optical signal and receiving the optical signal penetrating through the through holes.
 16. The apparatus according to claim 15, wherein the transmissive optical detector comprises a photo-interrupter.
 17. The apparatus according to claim 16, wherein the photo-interrupter comprises a transmitting end for emitting the optical signal and a receiving end for receiving the optical signal.
 18. The apparatus according to claim 1, wherein the rotatable gap sensor comprises: a shaft; a roller, mounted on the shaft and rotated by the movement of the first sheet and the second sheet through contact with the first sheet and the second sheet; an encoding disk, mounted on the shaft and rotated in synchronicity with the roller, the encoding disk being provided with a plurality of reflective blocks; and a reflective optical detector, disposed on one side of the encoding disk, for emitting an optical signal and receiving the optical signal reflected by the reflective blocks.
 19. The apparatus according to claim 18, wherein the reflective optical detector comprises a transmitting end for emitting the optical signal and a receiving end for receiving the optical signal. 